Poles are commonly used for mounting bird feeders and birdhouses, as well as other animal feeders and habitats. A common nuisance associated with such uses is climbing of the pole and infiltration of the feeders or habitats by unwanted animals, such as squirrels. Various guards and mechanisms have been proposed over the years to deal with this nuisance.
An example of one such mechanism can be found in U.S. Pat. No. 4,031,856 (the '856 patent), the contents of which are hereby incorporated by reference in their entirety. A post according to the '856 patent includes an elongated sleeve slidably disposed thereabout. The sleeve is attached to a cord that traverses a pulley near the top of the pole and is connected to a counterweight insider the pole. When a squirrel reaches the sleeve while climbing the pole, the weight of the squirrel overcomes the counterweight. As a result the sleeve moves downward to prevent the squirrel from continuing up the pole.
While effective in principle, the pole of the '856 patent has some shortcomings. For instance, the counterweight acts asymmetrically on the sleeve, resulting in increased friction between the sleeve and pole. Additionally, the cord is exposed in a position where it may be grasped by a squirrel, as well as being more susceptible to decay due to environmental factors.